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XR8fella · 09-26-2002, 17:53

hi guys and gurls,

just a question i have to clear up something i have been wondering.

Someone i know has a CV8 Munro, and was at a performance place, and they said that autos get 12% less RWKW than a manual. But didnt explain why !

Does this sound right, or is it right. Because at the flywheel a manual and auto (std ofcourse) would be the same, once the power hits the wheels and looses 12% is what confuses me, i gather an auto will be a tad slower than a manual. but anywho, can someone clear this up for me ????

ta

Luke

EDXR8 · 09-26-2002, 18:14

Auto's loose more through friction than manuals. Manuals loose around 20-25% and autos around 30-35%.

BRING_BACK_XF · 09-26-2002, 19:56

Autos have epicyclic (or "planetary") gear trains which have more teeth meshing together than your standard manual gearbox. This creates more friction which means power loss. Also, the torque converter generates a lot of heat which means power loss.

Rollin · 09-27-2002, 07:28

autos have more internal friction, as others have said, but also they have an oil pump which forces oil into the converter and around the gearbox, this steals power, also auto oil pressure is used to engage the clutches and bands in the gearbox, so some power loss is present due to the restriction of flow as the clutches engage etc.

also just the friction of the oil flowing in the converter and the relative movement of the impeller and turbine in the converter has a 'shearing' effect, which also takes power.

i dont think i have forgotten anything...
also

09-27-2002, 18:49

Just one last thing for all those auto owners out there that now feel let down. When out on the highway the auto locks up the tourque converter for later models there by reducing the auto's drag on the car and actualy getting better fuel economy than the manual gearboxes. :)
Not by much but we auto owners needed some good news to post. :)

cArSiK · 09-28-2002, 05:34

Quote:

Originally posted by magoo
Just one last thing for all those auto owners out there that now feel let down. When out on the highway the auto locks up the tourque converter for later models there by reducing the auto's drag on the car and actualy getting better fuel economy than the manual gearboxes. :)
Not by much but we auto owners needed some good news to post. :)

how do they manage better fuel economy with the lock-up TC compared to manual wouldnt it be the same with no rev;s slipping with either tranny?

The XR6T apparently is heaps better in auto than the manual accordiny to wheels so theres some more good news for auto owners magoo.....

09-28-2002, 07:54

From what I was told by my mechanic when in overdrive or top gear in the auto and crusing on the open road the tourque converter locks up there by making your final drive gear basicaly a straight through connection.
In all other gears the converter is still draining power to keep the auto hydrolics pressurised to be ready for any gear change up or down as the car may require.
I don't know if i have explained this verry well but that is how I understand it.
As to the XRT that would seem a fair point as with a manual and that much power bad driving habbits could realy place some strain on your drivetrain but I haven't done much homework on them yet I will wait till they are aval to test drive myself. :) cannot wait for that.

WBT56 · 09-30-2002, 01:34

Quote:

Originally posted by magoo
From what I was told by my mechanic when in overdrive or top gear in the auto and crusing on the open road the tourque converter locks up there by making your final drive gear basicaly a straight through connection.
In all other gears the converter is still draining power to keep the auto hydrolics pressurised to be ready for any gear change up or down as the car may require.

Untrue, as a) They are an overdrive auto, so top gear is not a direct coupling, and
b) The pump is still running to maintain clutch pack pressure, which is where a lot of the heat (bye bye hp) is produced. (Try and find a good hp commodore that hasn't fried a 3/4 clutch pack.)